Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.71	3.515%	$226.3977	$226.40	$226.40	$226.40
Purchase #2	$248.61	4.783%	$260.501	$260.50	$260.50	$260.50
Purchase #3	$99.75	9.840%	$109.5654	$109.57	$109.55	$109.60
Purchase #4	$89.79	9.791%	$98.5813	$98.58	$98.60	$98.60
Purchase #5	$38.62	13.422%	$43.8036	$43.80	$43.80	$43.80
Purchase #6	$41.87	8.514%	$45.4348	$45.43	$45.45	$45.40
Purchase #7	$172.31	12.570%	$193.9694	$193.97	$193.95	$194.00
7 purchase totals =	$909.66		$978.2532	$978.25	$978.25	$978.30